DESCRIPTION: The discovery of two novel yeast proteins, Duo282p, an essential spindle component, and Jsn1p, a protein that appears to influence microtubule dynamics and is enriched on microtubule affinity columns, provides unique opportunities to determine how accessory proteins regulate the dynamics of microtubule assembly in vivo. In addition, a third protein has been discovered which appears to provide a functional link between the microtubule and actin cytoskeletons during mitosis. This protein, Cor1p apparently serves as a link between microtubules and the cortical actin cytoskeleton during spindle orientation. The focus of this proposal is to investigate the mechanisms by which these novel proteins influence microtubule dynamics and spindle function. The specific aims are to: (1) elucidate the nature and function of Cor1p's interaction with the actin and microtubule cytoskeletons and to genetically and biochemically identify proteins which interact with yeast Cor1p; (2) determine the specific function of yeast Duo282p in spindle function and assembly and determine the nature of its interaction with spindles; (3) elucidate the role of Jsn1p in regulating microtuble dynamics by identifying proteins which function with or in parallel with Jsn1p. In total, these studies will define components of the microtubule and actin cytoskeletons that are required to ensure proper chromosome inheritance.